Police were called at approximately 11:30am on Friday, 10 September after a woman in her 20s was approached by a man in Ingrebourne Valley in Hornchurch Country Park.
It was reported that she was sitting on a bench when he came up from behind and placed a metal chain around her neck. The victim was able to free herself and ran out of the park.
The suspect is described as being a black man, who was dressed in dark clothing and wearing smart pointed shoes. It is thought he had slicked back black hair, with a silver streak.
PC Andy Tyler, from the local policing team in Havering, said: “This was a terrifying attack on a lone woman and I know it will cause concern among the wider community.
“We have increased patrols in the area since the incident and I can assure you that we are doing all we can to track down the man responsible.”
Anyone who recognises the man in the image is asked to call police on 101 or tweet @MetCC quoting CAD 2976/10Sep.
Information can also be provided anonymously to the independent charity Crimestoppers on 0800 555 111.